1. Field of the Invention
The present invention relates to a method for controlling washing in a washing machine, and more particularly, to a method for controlling washing, in which a total amount of laundry and washing water in a drum is determined before starting the washing.
2. Discussion of the Related Art
In general, there are drum type washing machines and upright type washing machines. For better understanding of current washing methods, a system of the drum type washing machine will be explained as an example. FIG. 1 illustrates a cross section of a related art drum type washing machine.
Referring to FIG. 1, a tub 3 is fitted inside of a cabinet 5, and a drum 9 is fitted inside of the tub 3. The drum 9 is connected to a motor 6 via a drum shaft 13 for transmission of driving power to the drum 9. The drum shaft 13 has bearings 12 on both ends, and there is a bearing housing at a central part of a rear wall of the tub 3 for supporting the bearings 12. There is a stator 7 fixed to the rear wall of the tub 3, and there is a rotor 8, which forms a direct coupling type motor 6 together with the stator 7, coupled to the drum shaft 13. The drum 9 is directly connected to and rotates with the rotor 8.
A door 1 is fitted in a front part of the cabinet 5. A gasket 2 is fitted between the door 1 and the tub 3. There are hanging springs 4 between an inside top surface of the cabinet 5 and an upper part of an outside circumference of the tub 3, for supporting the tub 3. There is a frictional damper 10 between an inside bottom surface of the cabinet 5 and an outside bottom surface of the tub 3 for attenuating vibration of the tub 3. There is a motor sensor 11 fitted to one side of the motor 6 for detection of a number of revolutions of the rotor 8.
After laundry is placed into the drum 9, the related art drum washing machine 9 detects an initial load by means of an electric load on the motor 6 during rotation of the drum 9. Water is supplied to the drum 3 according to the initial load detected. As the laundry absorbs water, the water supply is repeated during a predetermined time period. If the water does not fill the drum to a certain level, water is re-supplied until the level is reached. If the laundry absorbs more water, the water level may fall below the certain level, water is re-supplied. Water resupply occurs only during the predetermined time period. After the laundry absorbs the water and the washing water is filled and remains above the certain level of the drum 9, the laundry is washed according to the laundry having the water absorbed therein and the washing water amount. In determination of a final laundry load, the final laundry load is determined to be heavy if a number of water resupply times counted during the water supply period is greater than a predetermined number of times (for an example, 10 times), and to be light if a number of water resupply times counted during the water supply period is fewer than the predetermined number of times. According to this, the washing machine carries out washing following a washing algorithm suitable to the final load.
However, the determination of the final washing load with reference to the number of water resupply times only causes a problem of inaccurate detection of the final washing load. That is, each type of laundry e.g., cotton fabric, or wool fabric has different water bearing property (i.e., a water absorption rate and a maximum water bearing quantity). Therefore, not only the number of water resupply times, but also the final washing load, vary with the types of laundry and ratios of the types of laundry in the initial washing load, even if the initial washing load (an amount of laundry before water supply) is the same. Moreover, the water bearing property may vary the number of water resupply times for the final washing load. Eventually, in the related art process, the final washing load is mis-detected because such different properties of the mixed-type laundry is not taken into account, leading to a washing process having a washing algorithm inconsistent with an actual washing load.
For an example, it may be determined that the laundry has a heavy washing load due to the number of water resupply times is greater than the predetermined number of times even if an actual final washing load is light. In this instance, because the light washing load proceeds according to a washing algorithm for the heavy washing load, an unnecessary excessive load may be placed on the motor causing elevation of a temperature and a reduced lifetime of the motor. On the contrary, when the heavy washing load is wrongly determined to be a light washing load because the number water resupply times is below the predetermined number of times, the quality of the washing may be poor.